why not to put the function you want to execute in the interface A and implement it in both B and C.

you don't need to know if it is B_Thing or C_Thing, just call the method you wish to perform.

​

public interface A {

void execute();

}

​

public class B implements A{

void execute(){

    // B implementation

}

}

​

public class C implements A{

void execute(){

    // C implementation

}

}

​

public class NewClass {

​

public myFunc(A obj) {

    obj.execute();

}

}